Storage tank

ABSTRACT

A storage tank for storing liquid is adapted for construction in soil having a high-water table. The tank has sidewalls and a floor with the upper level of the floor being set below the height of the water table in the soil. To stabilize the tank and counter the effect of the uplift of the water in the soil, a ballast voided fill is placed within the tank.

[451 Feb. 1,1972

United States Patent Shelander [56] References Cited UNITED STATESPATENTS [54] STORAGE TANK [72] Inventor: Charles P. Shelander, DixHills, N.Y.

[73] Assignee: Preload Company, Inc., Garden City, N.Y.Rohren.......................................6l/.5

[22] Filed: Feb. 19, 1970 Primary Examiner-J. Karl Bell AttorneyCurtis,Morris & Safford 21 Appl. No.:

ABSTRACT A storage tank for storing liquid is adapted for constructionin soil having a high-water table. The tank has sidewalls and a floorwith the upper level of the floor being set below the height of thewater table in the soil. To stabilize the tank and counter the efiect ofthe uplift of the water in the soil, a ballast voided fill is placedwithin the tank.

3 Claims, 2 Drawing Figures PATENTED FEB I 1972 INVENTOR CHARLES P.SHELANDER BY 7 7m {Maj ATTORNEYS STORAGE TANK BACKGROUND OF THEINVENTION This invention relates to tanks for storing liquids, and moreparticularly to tanks which are placed in soils having highwater tableswith the upper surface of the tank floor at an elevation below that ofthe water table.

It is often necessary to place liquid storage tanks, such as those usedin water supply systems and the like, on land with high-water tables. Awater table is the natural height or elevation of water in the soil inrelation to the top or ground line of the land. A high-water table isone where the water is very close to the surface. Often times forasthetic purposes or for engineering reasons it is necessary toconstruct tanks so that the floor of the tank is at an elevation belowthat of the water table. When tanks are so constructed the hydrostaticpressure caused by the water table has a tendency to force the floorupwardly. This uplift effect can cause substantial damage to the tankunless adequate precautions are taken. One solution would be to providean extremely heavy and thick concrete floor to counterbalance theuplift. In essence, the thickened floor serves as a counterweight toovercome the hydrostatic head of the water table. However, such asolution is too costly and reduces the storage volume of the tank.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a ballast system for tanks built in regions having high-watertables so as to eliminate the necessity for costly thickened floors. Itis a further object of the present invention to provide a tankconstruction so that the ballast system does not substantially reducethe storage capacity of the tank.

In the present invention the ballast which is used is of a rock-filledtype and extends to a height sufficiently above the floor surface tocounteract the uplift effect of the water table.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a tankin accordance with the present invention; and

FIG. 2 is a sectional view showing the tank construction and ballastsystem in relationship to the surrounding soil area and the water tableof the soil.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Referring to the drawings, atank in accordance with the present invention is shown. The tank 10includes a foundation 12 of suitable reinforced concrete and which isintegrally connected to a reinforced concrete floor 14. Supported on thefoundation 12 is a reinforced concrete core wall 16. The wall 16 is seton a rubber pad of suitable elastomeric material so as to permit inwardmovement of the wall 16 during prestressing of that unit. This type oftank construction is more fully illustrated and discussed in US. Pat.No. 2,932,964, issued Apr. 19, 1960.

To insure the watertight construction of the tank where the wall 16 issupported on the pad 18, a continuous water stop 20 is provided. Afterthe tank wall 16 has been erected in place it is advantageouslyprestressed by means of tendons 22 which are covered over by a suitablecover coat 24 of cementious material. Flow of liquid into and out of thetank is provided by means of a conduit line 26. The inlet and outletline 26 is preferably encased in concrete 29 to strengthen it againstpossible damage. Surrounding the inlet portion of the line 26 is aperforated concrete cylinder 30 which in the illustration is a concretepipe. Placed on the upper surface of the floor 14 and surrounding thecylinder 30 is rock ballast 32. From the top surface 34 of floor 14 tothe top surface 36 of the ballast 32 is a distance which has beenindicated as Hr. As shown in FIG. 2, the distance from surface 34 to thewater table W/T in the surrounding soil E is designated Hw. It will benoted that the water table W/T is below the ground line G/L of thesurroundin earth.

In or er to determine the height of the rock ballast the followingforrnula may be used:

Hr=(62.5/200) Hw 62.5 is the approximate weight per cubic foot of waterwhile 200 is the approximate weight of a cubic foot of rock. The formulamay be more empircally written as:

Advantageously the ballast rock 32 permits the voids between theindividual rocks to be used as a storage area for liquid in the tank.Accordingly, it is only the solid portion of the ballast which isdeducted from the interior storage volume of the structure 10.

In order to clean the ballast 32 of any silt which may settle therein, abackwashing system may be utilized. To do this liquid is pumped inthrough the line 26 causing any deposits within the ballast to beflushed upwardly. It is then possible to flush away any silt by means ofhigh-pressure hoses in a routine fashion.

If desired, a silt ring 38 may be provided in connection with the line26 to prevent the entry of silt into the line.

While the present invention has been disclosed in the illustratedembodiment as applying to a soil with a high-water table, it may also beutilized as a precaution and safety feature where the tank is subject topossible flooding. In that case Hw would be determined as the height ofhigh water above the surface 34.

What is claimed:

1. A storage tank for storing liquids and built on soil having a heightwater table, said tank including a cylindrical concrete sidewall andfloor, the floor being placed at an elevation lower than that of thewater table, drainage means connected to said tank for removing liquidtherefrom, a voided rock ballast fill within the tank and resting on thefloor, said rock ballast fill being disposed within said storage tank toa level less than the height of said sidewall so that the upper portionof said storage tank is free of rock ballast till, the weight of saidfill being sufficient to overcome substantially and equalize the uplifteffect of water in the soil against the bottom of the floor, the ballastfill having sufficient voids to store liquid whereby the storage volumeof the tank is only reduced by the solid portion of the fill.

2. A storage tank for storing liquids as defined in claim 1 wherein theheight of the fill above the upper surface of the floor is at leastabout 0.3 the height of the water table above the upper surface of thefloor.

3. A storage tank for storing liquids as defined in claim 1 and furtherincluding a screening device separating the ballast fill from the tankdrainage means.

1. A storage tank for storing liquids and built on soil having a heightwater table, said tank including a cylindrical concrete sidewall andfloor, the floor being placed at an elevation lower than that of thewater table, drainage means connected to said tank for removing liquidtherefrom, a voided rock ballast fill within the tank and resting on thefloor, said rock ballast fill being disposed within said storage tank toa level less than the height of said sidewall so that the upper portionof said storage tank is free of rock ballast fill, the weight of saidfill being sufficient to overcome substantially and equalize the uplifteffect of water in the soil against the bottom of the floor, the ballastfill having sufficient voids to store liquid whereby the storage volumeof the tank is only reduced by the solid portion of the fill.
 2. Astorage tank for storing liquids as defined in claim 1 wherein theheight of the fill above the upper surface of the floor is at leastabout 0.3 the height of the water table above the upper surface of thefloor.
 3. A storage tank for storing liquids as defined in claim 1 andfurther including a screening device separating the ballast fill fromthe tank drainage means.